What is a blockchain oracle?

What is a blockchain oracle?

Imagine a world where your insurance payout for a delayed flight is immediate, where your online games are influenced by real-world events, or where your digital artwork evolves based on the day's weather. Sounds futuristic, right? Well, this is no longer the stuff of science fiction, but the exciting reality being enabled by blockchain technology and, more specifically, an often-overlooked component known as "blockchain oracles".

These oracles, despite what their mystical name might suggest, are not fortune-tellers but trusted data feeds that provide blockchains with information from the real world. They serve as the critical link between the deterministic world of blockchain and the dynamic and complex world we inhabit. Without these oracles, the blockchain is like an island - isolated and disconnected.

In this blog post, we'll delve into the intricacies of blockchain oracles, how they work, and their crucial role in bridging the gap between the on-chain and off-chain worlds. We'll cover the different types of oracles, explore their benefits, drawbacks, and take a closer look at their fascinating applications in areas such as insurance, supply chain management, decentralized finance, prediction markets, real estate, gaming, and the rapidly evolving world of Non-Fungible Tokens (NFTs).

Whether you're a blockchain enthusiast, a curious technophile, or a complete beginner, this guide will help you understand the integral role of blockchain oracles in the digital revolution we're experiencing. So, buckle up and let's embark on this exciting journey together!

What is a blockchain oracle?

A blockchain oracle is a system that provides external data to smart contracts on the blockchain. In the context of blockchains and cryptocurrencies, an oracle is an agent that finds and verifies real-world occurrences and submits this information to a blockchain to be used by smart contracts.

Smart contracts are self-executing contracts with the terms of the agreement directly written into lines of code. However, these smart contracts are not capable of interacting with data outside of their network. That's where oracles come into play.

There are several types of oracles based on the kind of data they provide, the source of data, and the level of centralization:

  1. Data Type Based Oracles: These include price oracles, weather oracles, etc. They fetch and provide data related to specific fields.
  2. Source Based Oracles: Software oracles provide data from online sources, while hardware oracles are sensors or other physical devices that feed data directly into the blockchain.
  3. Centralization Based Oracles: Centralized oracles are managed by a single entity, and decentralized oracles are managed by multiple entities to reduce the risk of manipulation.

Oracles are crucial for the functioning of many decentralized applications (DApps) on blockchain networks. However, they can be a point of vulnerability because they introduce a level of trust into an otherwise trustless system. If an oracle provides false or manipulated information, it can lead to incorrect outcomes for the smart contracts relying on it. This issue is known as the "oracle problem," and numerous projects are working on solutions to mitigate this potential issue.

What is the oracle problem, and how can it be solved?

The oracle problem is a major obstacle in the world of blockchain and smart contracts. Because blockchains cannot access data outside their network, they rely on oracles to provide real-world data. However, this reliance introduces a potential point of failure. If the oracle is compromised or feeds incorrect data to the smart contract, it can lead to undesired consequences.

For instance, consider a flight insurance smart contract that automatically pays out if a flight is delayed or cancelled. The smart contract relies on an oracle to provide accurate flight status data. If a malicious actor gains control of the oracle and feeds incorrect data, it could lead to fraudulent payouts or prevent legitimate payouts.

A key challenge in addressing the oracle problem is ensuring data integrity while maintaining the decentralized and trustless nature of the blockchain. Here are some strategies:

1. Multiple Oracles: Instead of relying on a single oracle, the smart contract can be designed to require data from multiple oracles. The data received is then aggregated or a consensus mechanism is applied to determine the final input for the smart contract. This approach can reduce the risk of a single point of failure, but it's not foolproof, as multiple oracles could still be compromised.

2. Decentralized Oracles: In this model, the data input duty is given to a network of decentralized nodes, which act as oracles. This reduces the risk of centralized control or manipulation. Chainlink is a notable project that implements this approach.

3. Trustworthy Data Sources: This method involves using oracles that source data from reputable and verified sources. While this approach can improve the reliability of data, it doesn't fully align with the principle of decentralization.

4. Economic Incentives and Penalties: Some systems use economic incentives to reward accurate data provision and penalties for incorrect data. Augur, for example, uses a reputation token to incentivize truthfulness.

5. Use of Trusted Execution Environments (TEEs): TEEs like Intel's SGX can help mitigate the oracle problem by running the oracle code in a secure environment that is resilient to tampering, even by the operators of the oracle themselves.

However, each of these solutions has its trade-offs and none of them completely solves the oracle problem. It remains an active area of research in the blockchain community.

What are the types of oracles, and their pros & cons?

Sure, blockchain oracles can be categorized based on several different criteria such as the type of data they provide, the source of data, and the level of centralization. Here's a summary of some common types and their respective advantages and disadvantages:

1. Software Oracles:


  • They can provide a wide range of data from online sources, such as prices, weather information, flight statuses, etc.
  • They can automate responses to certain online events or conditions.


  • They are vulnerable to online attacks or manipulations.
  • The reliability of data depends on the source from which it's fetched.

2. Hardware Oracles:


  • They can provide real-world data that software oracles can't, such as temperature readings from a physical location, supply chain data from RFID tags, etc.


  • They are susceptible to tampering in the real world.
  • Technological limitations and compatibility issues may affect the data they provide.

3. Inbound Oracles:


  • They provide external data to smart contracts, enabling them to interact with the outside world.


  • Their performance and reliability are crucial for the correct execution of smart contracts.
  • They might provide incorrect data either by mistake or malicious intent.

4. Outbound Oracles:


  • They allow smart contracts to trigger events in the outside world.


  • The actions they trigger (like sending an email or text message) could fail without the smart contract knowing.

5. Centralized Oracles:


  • They are simpler and easier to set up.
  • They may provide more timely and accurate data if run by a reputable entity.


  • They are a single point of failure. If the oracle fails, the smart contract that relies on it also fails.
  • They might be biased or manipulated.

6. Decentralized Oracles:


  • They reduce the risk of manipulation as data is sourced from multiple entities.
  • They are more reliable and resilient as the failure of one oracle doesn't halt the entire system.


  • Consensus mechanism might slow down the process.
  • Disagreements among the oracles can delay or complicate decision-making.

Each type of oracle has its own use cases and areas where it performs best. The choice of oracle depends on the specific needs of the smart contract and the nature of the data it requires.

Why do we need decentralized oracles?

Decentralized oracles in the blockchain context aim to solve the "oracle problem" – the vulnerability and trust issues associated with using a single, centralized oracle for external data input into smart contracts.

In a decentralized oracle system, instead of a single oracle providing data, multiple independent oracles collectively provide data. This data is typically aggregated or a consensus mechanism is used to determine the final value that gets fed into the smart contract.

Decentralization brings numerous benefits:

  1. Reduced Manipulation: By utilizing multiple sources for data, the system becomes more resilient to manipulation. A malicious actor would have to compromise multiple oracles instead of just one, which is significantly more difficult.
  2. Increased Availability: With multiple oracles, the system becomes more reliable. If one oracle fails or goes offline, others can still provide the necessary data, minimizing the risk of system-wide failure.
  3. Improved Accuracy: Through consensus algorithms, decentralized oracles can often provide more accurate data. If one oracle provides incorrect data, it will likely be outvoted by the others.
  4. Aligns with Blockchain Principles: Decentralization aligns better with the principles of blockchain, such as trustlessness and decentralization. It reduces the need to trust a single oracle or data source.

There are several projects that implement decentralized oracle systems:

  • Chainlink: Perhaps the most well-known decentralized oracle, Chainlink uses a network of independent node operators that fetch and deliver data for smart contracts. Chainlink incentivizes honesty and accuracy through a reputation system and staking mechanism.
  • Band Protocol: Similar to Chainlink, Band Protocol provides a framework for decentralized data governance. It uses a delegated proof-of-stake consensus mechanism to ensure data integrity.
  • Tellor: Tellor is a decentralized oracle that uses a proof-of-work system to secure its network. Miners compete to submit data points to the network, and are rewarded with Tellor's native token for their work.

These are just a few examples. It's important to note that while decentralized oracles do improve the security and reliability of data for smart contracts, they do not completely eliminate the oracle problem. Ensuring the trustworthiness and accuracy of off-chain data remains a challenging issue in the blockchain space.

5 Use Cases for Blockchain Oracles

Blockchain oracles have a broad range of applications, particularly because they allow smart contracts to interact with data outside their blockchain. Here are five potential use cases:

  1. Insurance Smart Contracts: For insurance policies based on objective conditions, such as weather events or flight delays, oracles can provide the necessary real-world data. For instance, an oracle could inform a smart contract of a flight delay, which would automatically trigger a payout to the insured party.
  2. Supply Chain Management: Oracles can be used to track and verify the location of goods as they move along a supply chain. RFID tags or GPS data can be used by oracles to update a blockchain-based supply chain system.
  3. Decentralized Finance (DeFi): DeFi protocols often require real-time information on things like currency exchange rates, commodity prices, or interest rates. Oracles can provide this data, enabling functionalities like automated loans or leveraged trading.
  4. Prediction Markets: Prediction markets like Augur depend heavily on oracles. Users bet on the outcomes of future events, and oracles are needed to report what actually happened so that the smart contracts can resolve bets correctly.
  5. Real Estate: In the case of tokenized real estate and land registries, oracles can provide necessary data such as verifying the completion of a payment or transfer of ownership, or providing real-world property values to adjust prices on the blockchain.

In all these cases, the oracle provides a critical bridge between the deterministic world of the blockchain and the variable, complex world outside the blockchain. It's crucial to note, though, that the reliability of the oracle is a critical factor in these use cases.

Concluding thoughts

Blockchain oracles are indeed the unsung heroes in the blockchain ecosystem. By bridging the gap between the on-chain and off-chain worlds, they breathe life into smart contracts, enabling them to interact with real-world data and trigger off-chain events.

From the dynamic world of gaming and NFTs to the practical realms of insurance, supply chain, and decentralized finance, the applications of blockchain oracles are broad and ever-growing. However, they're not without their challenges. Ensuring the reliability and security of these oracles is paramount to maintaining trust and functionality in the systems that rely on them.

As we look forward to a future where blockchain technology permeates more aspects of our lives, we must also anticipate and work towards innovative solutions for the so-called "oracle problem." The journey ahead is thrilling, filled with untold possibilities. With the relentless pursuit of knowledge and innovation, there's no doubt that we're on the cusp of a new digital dawn, with blockchain oracles lighting the way.